Filling the knowledge gap: from seismic risk maps towards nationwide digital twins

Recent seismic events underlined the inherent vulnerability of the built environment to earthquakes. Older buildings in seismic-prone countries, constructed before modern seismic codes, lack adequate structural detailing, causing poor behaviour during seismic events. Several risk maps – combining the seismic hazard and the vulnerability of the building stock - have been developed to aid decision-makers in implementing riskreduction strategies by targeting the vulnerability of structures in seismic-prone areas. Although these maps can be of great value in managing risk from a local municipality to a national scale by providing crucial information, they are often limited in spatial resolution, which hinders their ability to identify and address specific building-to-building vulnerabilities accurately. However, the recent advancement in computing infrastructures made possible the transition from low-resolution – yet computationally efficient - vulnerabilitybased models to the development of more advanced and detailed Digital Twins. These Digital Twins can be used to assess the seismic risk by employing simplified-to-refined seismic response analyses. Still, such models need to be developed with a limited amount of data concerning the building stock which usually is not well documented. However, following an iterative and knowledge-based incremental approach, the data regarding the buildings can be updated as they become available, reducing the uncertainties of the results at each additional information-gathering step. This paper intends to address this knowledge gap by introducing a framework to assess seismic risk at the territorial - from urban-to-national - scale. The proposed procedure provides an initial – mechanically based - estimation of both life-safety and economic losses for a large set of individual buildings. Importantly, the procedure not only provides anticipated values but also offers a range/domain of expected outcomes, enhancing the understanding of seismic risk of decision-makers and stakeholders. Through an illustrative application, this paper serves as a proof of concept, highlighting the framework's potential while also spotting the existing challenges and limitations that must be addressed to facilitate widespread implementation at a national level. The information obtained can be used to guide stakeholders and decision-makers into further data collection efforts and, at the same time, to the definition of risk mitigation policies.